Process for making dye transfer copies of improved quality

ABSTRACT

High color density, high resolution and wash resistant dye transfer copies are obtained in a solvent transfer duplication process by utilizing a copy sheet formed with a dye receiving coating of reduced porosity and limited solvent absorption relative to the uncoated surface of the copy sheet. The coating includes a smooth binder containing a dye absorber. In addition to yielding higher image quality, the coating acts as a solvent barrier so that both sides of the copy sheet can be used for duplication.

United States Patent [191 Gaynor et al.

[ 1 PROCESS FOR MAKING DYE TRANSFER COPIES OF IMPROVED QUALITY [75] Inventors: Joseph Gaynor, Cleveland, Ohio;

Yoshikazu Yamada, Irvine; Joseph Tat-l-Iin Sund, Los Angeles, both of [21] Appl. No.: 373,833

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 59,392, July 30,

1970, abandoned.

[52] U.S. C1. 101/472, 101/473, 117/155 R, 117/155 UA [51] Int. Cl. B4lm 5/00 [58] Field of Search 101/468, 469, 470, 472, 101/473; 117/155 R, 155 UA [56] References Cited UNITED STATES PATENTS 1,795,378 3/1931 Ritzerfeld 101/472 2,088,417 7/1937 Hoskins 101/469 2,287,161 6/1942 Ball 117/155 R 2,582,932 1/1952 Lustbader.... 101/473 2,583,274 1/1952 Niles ll7/l55 UA 3,034,428 5/1962 Ellam 101/468 Oct. 8, 1974 3,170,395 2/1965 Gundlach et a1. 101/470 3,478,716 1l/l969 Weber ll7/l55 R OTHER PUBLICATIONS Dictionary of Paper, 2nd ed., 1952, American Paper & Pulp Assn. pp. 76, 77, 78, 154 & 155.

Casey, J. P., Pulp & Paper Making, 2nd ed., Vol. III, 1961, Interscience Publishers, Inc. p. 1848.

Bureau, W. P., Papers & the Fluid Duplicating Process, Graphic Arts Monthly, Vol. 35, No. 7, July 1963, pp. 80, 90, 92, 94.

Primary Examiner-David Klein Attorney, Agent, or Firm-Nilsson., Robbins, Bissell, Dalgran & Berliner 5 7] ABSTRACT High color density, high resolution and wash resistant dye transfer copies are obtained in a solvent transfer duplication process by utilizing a. copy sheet formed with a dye receiving coating of reduced porosity and limited solvent absorption relative to the uncoated surface of the copy sheet. The coating includes a smooth binder containing a dye absorber. In addition to yielding higher image quality, the coating acts as a solvent barrier so that both sides of the copy sheet can be used for duplication.

12 Claims, 6 Drawing Figures PROCESS FOR MAKING DYE TRANSFER COPIES OF IMPROVED QUALITY CROSS REFERENCE TO RELATED APPLICATION This application is a Continuation-ln-Part of Application Ser. No. 59,392, filed July 30, 1970, entitled DYE TRANSFER COPIES OF IMPROVED QUALITY, now abandoned.

FIELD OF THE INVENTION The field of art to which the invention pertains, includes the field of planographic printing processes utilizing soluble dye transfer, and coated copy paper.

BACKGROUND AND SUMMARY OF THE INVENTION Soluble dye transfer or spirit duplicating processes are characterized by the formation of a master surface, in the form of a sheet or otherwise, which carries an image typically formed of an alcohol soluble dye impregnated in wax, or the like. Copy paper is brought into contact with the master image and solvent which has been previously spread on the copy paper. Such a process allows part of the dye in the master image to be dissolved and transferred to the copy paper. As a result of solvent penetration, carrying the image well into the sheet, only one side of the sheet can be effectively used for duplication. Typically, the dye may be crystal violet and the solvent methanol, but such materials are only exemplary and a wide variety of dyes, solvents, waxes, etc. suitable for the practice of such processes are known to the art.

It has long been believed that soluble dye transfer processes have inherent limitations of low resolution, low image density and short master life, although a number of approaches have been utilized to improve these characteristics. Among the early improvements were the use of materials known as mordants which were coated on the copy paper before or after dye transfer. The mordanting chemical reacts with the transferred dye to fix the dye to the copy paper. Early disclosures of such mordanting processes can be found in US. Pat. Nos. 749,684, 2,088,417, 2,222,973, 2,288,389, 2,332,696 and 2,337,737. Various image enhancing materials have been applied to the master sheet, as disclosed in US. Pat. Nos. 778,647, 2,163,934, 2,925,355, and 3,226,252. Other disclosures of general interest can be found in US. Pat. Nos. 1,795,378, 2,287,161, 2,582,932, 2,583,254, 3,034,428, 3,170,395, 3,343,973, 3,359,900,

3,458,339, and 3,478,716. Publications of general interest include: Dictionary of Paper, 2d ed. (1952) by American Paper and Pulp Assn. (pp 76, 77, 78, 154 and 155); Pulp and Paper Making, by J. P. Casey, 2d ed. (1961) Vol. III, Interscience Publishers, Inc., NY. (p. 1848) and Papers and the Fluid Duplicating Process by W. P. Bureau, Graphic Arts Monthly, Vol. 35, No. 7 (July, 1963), (pp. 88, 90, 92, 94).

Importantly, it has long been believed that a key method for improving the quality of copies is to simply increase the porosity of the copy paper to permit greater penetration of the dye-bearing solvent; see for example US. Pat. Nos. 2,288,389 and 2,337,737. This, of course, further decreases any ability to use both sides of the sheet for duplication.

The present invention provides soluble dye transfer copies having improved color density, resolution and wash resistance by utilizing a copy paper which is coated for better reception of the dye, but which coating actually and substantially limits the solvent absorption of the copy paper so as to reduce the penetration of dye-bearing solvent into the copy paper. The present invention thus represents a dramatic departure from heretobefore long held beliefs about the importance of deep dye penetration to high quality duplication. In fact, a limitation in solvent absorption, as compared with ordinary copy paper is required for proper operation of the present invention.

In particular, the improvement herein is obtained by providing a copy sheet base which is formed with a dye receiving coating of reduced porosity through its thickness (albeit the surface can be porous) and limited solvent absorption relative to the uncoated surface of the copy sheet, the coating including a smooth binder containing a dye adsorber. The adsor'ber is in the form of fine, particulate material which is chosen for its ability to adsorb dye molecules, rather than for any ability to react with them. The binder is chosen to fulfill a variety of purposes, one of which is to support the adsorbing particulate material, dispersed therethroughout, on the surface of the copy sheet base, and another purpose being to limit the penetration of the dye bearing solvent so that the dye is subject to little or no adsorption by the paper base, but is adsorbed on the particulate material. In this regard, the binder is sufficiently pene'trable by the dye solvent, such as methanol, as to allow the dye solvent to reach the particulate material, but the thickness of the binder coating and the relative solvent resistance are such that the solvent does not penetrate through to the paper base. In particular, the binder coating is about 0.1 mil to 1.5 mils thick and the binder material is characterized by initial 60 second methanol absorption per double sided area in the range of 1.5 to 8.0 mg/cm and this criteria will be amplified on below.

The coated surface can be calendered to reduce sur face porosity but some surface porosity may be desired to prevent horizontal dye spreading. importantly, the coating can be applied to one or both sides of the sheet and allows both sides to be used for duplication.

BRIEF DESCRIPTION OF THE DRAWINGS cess and duplication steps for paper coated on both sides.

DETAILED DESCRIPTION Referring initially to FIG. .1, there is schematically illustrated the preparation of copy paper for utilization in accordance with the present invention. Paper in the fonn of an elongate sheet 10 is fed. past a liquid coater 12 containing the coating materials in the form of an emulsified dispersion 14, as hereinafter described in more detail, whereupon a coating 16 thereof is deposited on the surface of the sheet 10. After drying, the coated sheet is passed between calendering rolls 18 and 20, as indicated by the arrow 22, whereupon it emerges with a smoother top surface 24. Thereafter the sheet 10 is cut to desired lengths and widths to form a plurality of copy papers. The paper constituting the sheet 10 can be any common, inexpensive grade of paper as convenient, the sheet 10 acting only as a base for the coating 16, which coating serves as the image receiving medium.

The coating 16 material is applied as an emulsion for minimum penetration of the coating 16 through the surface of the base paper 10. This can be contrasted with prior art methods which sought to obtain intimate contact between coating and paper fiber. In accordance with the present development, the coating is formed so as to act as a solvent barrier, preventing dyebearing solvent from contacting the fibers of the paper base. By so limiting penetration of the duplicating solvent, the quality characteristics of the duplicated image is defined only by the properties of the coating 16. Accordingly, it is the coating 16 which constitutes the copy surface rather than the surface of a paper copy sheet. The coating 16 comprises l a dye adsorber and (2) material forming a binder for the dye adsorber. The binder is formed from a water-insoluble emulsifiable material such as an organic polymer having certain solvent absorptive characteristics as will be defined more fully below. By applying the coating materials in the form of an emulsion, penetration of the coating 16 through the fibers of the base paper 10 is successfully limited.

Although the adsorptive nature of the copy sheet surface is radically changed, by appropriate calendering of the surface, the copy sheet can retain the feel, writability, handling and other mechanical characteristics of the original sheet. In particular, it is advantageous to use calendering rollers having a stipled nip on at least the roller surface contacting the copy sheet surface, and preferably on both roller surfaces. Calendering rollers having a cotton-steel nip, preferably a cottoncotton nip, provide the copy sheet surface with microroughness which aids in eliminating horizontal dye spreading. Copy sheets with such calendered surfaces look and feel like ordinary paper but microscopic examination reveals a textured surface. Generally, a calender nip should be used which will impart a textured surface having a continuous plurality of ridges defining discrete depressed regions about 0.1 to l2.5 microns deep, opposed portions of the ridges being spaced a distance of about 0.1 to 25 microns. Such surfaces can be characterized as having microporosity.

Referring now to FIGS. 2 and 3, there is schematically illustrated the manner of using a coated copy sheet in accordance with this invention. FIG. 2 illustrates the disposition of a copy sheet, including paper base 10 and coating 16, adjacent a dye transfer master sheet 26 such as utilized in a typical spirit duplicating process. The master sheet 26 includes an image layer 28 of wax or the like bearing a soluble dye and which is patterned in accordance with an image to be duplicated. The dye in the image layer 28 is generally an alcohol soluble dye as typically employed in a spirit duplicating process. Thus, among the dyes which can be utilized are methyl violet, crystal violet, the fuchsines, the magentas, the anthraquinones, and the like; aniline dyes, such as aniline blue, Victoria blue and orange, Nile blue, and the like; and azo dyes, such as Congo red, Bismarck brown, and the like.

In order to transfer dye material from the image layer 28 to the coating 16, a solvent for the dye is applied to the coating 16, just prior to contact thereof with the master sheet 26. Any of the common solvents for such purpose can be utilized and typically a volatile alcohol, such as methyl alcohol, is applied.

FIG. 3 schematically depicts the stage of duplication wherein solvent has been applied to the coating 16 which has thereafter been pressed into contact with the image layer 28. The solvent penetrates only partially into the coating 16, as indicated by the line 30, and carries with it dye 32 dissolved therein from the image layer 28. As schematically shown at 34, the transferred dye 32 is limited in penetration by the extent of penetration of the solvent line 30. As a result, solvent is spread in a thin layer, measured in microns, over the surface of the copy sheet, thereby severely limiting the opportunity for lateral diffusion. With ordinary copy sheets, the solvent may penetrate to the extent of 3.5-4 mils which provides a much greater opportunity for lateral diffusion. Furthermore, any dye transferred to the coating 16 is immediately adsorbed and thus sharply limited in lateral spread. As indicated at 36 and 38, lateral spread of the transferred dye 32 is substantially c0- terminous with the lateral extent of the corresponding portions of the image layer 28. The result is very high, previously unobtainable resolution.

Because the solvent residing on the copy sheet surface is available for dye extraction, greater extraction efficiency is obtained, allowing more copies from a master and/or more dye per copy. This balance can be controlled by modifications in the duplicating parameters, which was not before possible. Additionally, as a result of the limitation of penetration of the dye 32 into the coating 16, transferred dye 32 is localized and results in a much higher color density than heretobefore obtainable. Color density is also increased by the use of irregularly shaped, multi-faceted particles as dye adsorber which as a result of internal reflections and light scattering, yields substantially darker images. Further increase in color density is obtained by use of texturing calendering rollers as above described. The adsorbtivity of the dye adsorber also results in improved wash resistance of the image.

As dye adsorber, one can utilize any particulate material which can be dispersed throughout the binder and which is capable of adsorbing organic solventsoluble dyes. A particularly suitable class of adsorbers are the clays, notably the silicate pigments, such as kaolin, and components thereof such as kaolinite. While some of the clays useful herein contain sufficient impurities to provide mordanting sites for the transferred dyes, such property is not at all required for operation of the present invention which relies only on adsorbtion; indeed, kaolinite which is a particularly preferred adsorber does not mordant the dyes. To be most effective, the dye adsorber should be in the form of small particles. In general, particle size distribution between about 0.1 to about 25 microns is preferred. For example, Kaolinite UF, produced by the Georgia Kaolin Co., has a particle size distribution from about 1 micron down to less than 0.1 micron with an average particle size of about 0.2 micron. To aid in dispersing the adsorber particles, one may add a small amount of phosphate, e.g. 0.1-0.5 percent by weight, such as tetrasodium pyrophosphate or tributyl phosphate.

Materials constituting the binder are chosen on the basis of several criteria. A first criterion is that the material should be a water-insoluble organic polymer which either is formed emulsified or can be emulsified in water or other hydrophilic medium for application to the surface of the base paper. Such polymer dispersions, unlike natural and synthetic water-soluble binders such as casein and starch, do not appreciably penetrate the surface of the base paper. The highly mobile water phase of the emulsion appears to be selectively absorbed by a capillary action, leaving behind the polymer particles at the interface which unite to form a continuous binder for the dye adsorber. A wide variety of materials satisfy this first criterion, such as the acrylic resins, butadiene-styrene, butadieneacrylonitrile polymers and the like. See for example, the publication SYNTHETIC AND PROTEIN AD- HESIVES FOR PAPER COATING, Tappi Monograph Series No. 22, published by the Technical Association of the Pulp Paper Industry, New York, New York 1961 hereby incorporated by reference. A second criterion is that the binder material, when coated and dried have certain minimum and maximum solvent absorption characteristics. These characteristics, for purpose of the present invention, can be defined with respect to methanol absorption in accordance with the following procedure. A thin film specimen of the binder material is cut into various sizes, on a side about 1.5, 3.2 and 6.9 cm The cuts are weighed, dipped into methanol for 60 seconds and then air dried. While drying, and at one minute intervals, the weight of the cuts is determined. The average weight of methanol absorbed is then plotted against the average double sided area (i.e., the total area of both sides) of the cuts. The obtained data points are then connected and extrapolated to zero drying to obtain a weight/area ratio. This ratio can be termed the initial 60 second methanol absorption of the specimen.

In accordance with this criterion, the binder material should have an initial 60 second methanol absorption per double sided area in the range of 1.5430 mg/cm Thus, the organic polymer material constituting the binder should be such that, when solidified, the binder is relatively impermeable and insoluble to the dye transfer solvent. However, the material constituting the binder need not be solvent insoluble. The above criteria provide a binder which is wettable by the solvent so that dye may be sufficiently transferred thereto and through the surface into contact with the dispersed dye adsorber.

Each of the binder materials specifically listed above possess these characteristics and the characteristics for other materials can be readily determined by the foregoing absorption test. The acrylic polymers have been found to be particularly effective whereas polyvinyl acetate and polyvinyl alcohol have been found to be ineffective, the former being too absorptive and the latter insufficiently absorptive. Referring to FIG. 4, a plot such as described above was obtained for commercial grades of acrylic emulsion (sold by the Rohm and Haas Company under the trademark Rhoplex AC-6l,) polyvinyl acetate (sold by National Starch and Chemical Corporation under the trademark Resyn 1105) and polyvinyl alcohol (sold by E. I. DuPont de Nemours & Company under the trademark Elvanol 71-30.)

Upon extrapolation, the average initial second methanol absorption per double sided area was as follows:

acrylic emulsion 2.8 mg/cm polyvinyl acetate 1 1.2 mg/cm polyvinyl alcohol 1.3 mg/cm Accordingly, the acrylic emulsion is suitable for use as binder material whereas the polyvinyl acetate and polyvinyl alcohol are not suitable.

In general it is preferred to utilize an amount of dye adsorber sufficient to constitute with the binder a weight ratio of about 0.5:1 to about 15:]. As hereinabove noted, the binder acts as a barrier layer preventing the dye transfer solvent from reaching the fibers of the base paper. However, except as necessary to assure this property, as little binder material as possible should be utilized so as to avoid an inordinate increase in the weight of the copy paper. Generally, an amount of binder material to yield, with the dispersed dye adsorber, a coating of about 0.005 to about 0.08 ounces per square foot of coated surface is satisfactory and represents a coated thickness of about 0.1 mil to about 1.5 mils.

By preventing the penetration of the transferred dye into the paper base, the reverse side of the copy sheet can be used for additional duplication. Such doublcsided copying was not heretobefore feasible with spirit duplicating processes. In a further embodiment of the present invention, both sides of the copy sheet are coated, thereby enabling high quality images to be obtained on both sides with a minimum of visual interference. Referring to FIG. 5, a stage of production is illustrated wherein base paper 40 has had deposited thereon coatings 42 and 44 in the form of emulsified dispersions as described with respect to FIG. 1. After drying, the coated sheet 40 is passed between calendering rolls 46 and 48, as indicated by the arrow 50, whereupon it emerges with relatively smooth surfaces 52 and 54. In this case cotton-cotton nip calendering rollers 46 and 48 are used. Thereafter the sheet 40 is cut to desired lengths and widths to form a plurality of copy papers.

Referring now to FIG. 6, there is schematically illustrated the manner of using a doubly coated sheet. The copy sheet 40 is depicted with an image formed on one side 54 as defined by dye 56 transferred to the coating 44 in a manner similar to that depicted in FIG. 3. The reverse side 52 is then utilized by pressing it into contact with the image layer 58 on a spirit process master sheet 60. Processing solvent penetrates only partially into the coating 42, as indicated by the line 62, and carries with it dye 64 dissolved therein from the image layer 58. The transferred dye 64 is limited in penetration by the extent of penetration of the solvent line 62. The result is a copy sheet containing images on both sides, neither of which has extended into the sheet. Accordingly, neither image interferes with the other.

The following examples will serve to illustrate the invention.

EXAMPLE I A starting solution was obtained by adding 1.13 ml of Blancophor SBT 167 (an optical brightener produced by the General Aniline & Film Co.) to 225 ml of water and the solution was mixed with 100 grams of Kaolin N.F. (National Formulary), as adsorber, with agitation, until a uniform dispersion was obtained. 50 milliliters of Rhoplex AC-61 (an anionic acrylic resin emulsion containing 46-47 percent solids, produced by the Rohm & l-Iass (30.), as binder material, was then added and the resulting mixture was ball-milled with glass marbles overnight. The mixture was then coated on copy paper (produced by Bell & Howell Company under the trademark Dittcopy) to a dry coating of 0.5 mil, which increased the weight of a 500 sheet ream of 17 inch X 22 inch paper by 2 pounds, i.e., by about 0.025 ounces per square foot of surface.

A spirit process sheet of the type described in US. Pat. No. 3,706,276 was specially prepared to yield a master having a resolution of greater than eight line pairs per millimeter. Copies were made on uncoated Dittcopy paper and the paper coated as above. Print resolution on the coated Dittcopy paper was about 9-10 line pairs per millimeter while print resolution on the uncoated Dittcopy paper was about five line pairs per millimeter.

Coated paper prepared as above was calendered to a coating thickness of about three mil. Copies printed from the aforementioned master resulted in greater uniformity of the image.

As a further illustration of the dramatic improvement obtained herein, a thermally imaged master was prepared and placed in a commerical duplicating machine. Copy production was begun using conventional, uncoated Dittcopy paper, and 159 copies were run. The last copy was so weak in color density as to be unacceptable and under ordinary circumstances the master would no longer have been useful. Dittcopy paper coated in accordance with the foregoing example was then placed in the machine and additional copies run. The additional copies, made on the coated paper had greatly improved image density and were quite acceptable.

EXAMPLE II Dittcopy paper was coated in accordance with the method of Example 1 except that a 20 gram portion of the 100 grams of the Kaolin NF was replaced by 20 grams of titanium dioxide. Similar improvements in image resolution were obtained.

EXAMPLE III A coating was formulated by dispersing 24.0 grams of ultrafine Kaolinite UF (obtained from Georgia Kaolin Co.) in 35 mil ofa 1.3 weight percent aqueous solution of sodium tetraborate. l milliliters of Rhoplex AC-61 acrylic resin emulsion was added to the clay dispersion and ball-milled with glass marbles overnight. The formulation was coated on Dittcopy paper using a No. 16 Mayer bar, and then dried in an oven at 48C. Copies prepared by the first mentioned method in Example I had print resolutions of nine line pairs per millimeter.

EXAMPLE IV Dittcopy" paper was coated in accordance with the method of Example III except that 15 ml of a 10 percent aqueous solution of sodium thiosulfate was substituted for the sodium tetraborate solution of Example 111 and 7 ml of Rhoplex AC-6l was used rather than 10 ml as in Example III. Copies were produced having a print resolution of nine line pairs per millimeter.

EXAMPLE V A coating was formulated by dispersing 12 grams of Kaolinite UF in 15 ml of water. A solution of 2 grams of Methocel -HG (a hydroxypropylmethyl cellulose, produced by the Dow Chemical Co.) in 60 ml of water was added to the clay dispersion and ball-milled overnight. The Methocel was found to have an initial 60 second methanol absorption per double sided area of 7.4 mg/cm The formulation was coated on Dittcopy paper using a No. 16 Mayer bar and dried in an oven at 48C. Copies were prepared by the first mentioned method in Example I and had improved image quality in comparison to copies printed on uncoated Dittcopy" paper.

EXAMPLE VI A coating was formulated by dispersing 20 grams of Kaolinite UF in 15 ml water. 5 milliliters of Rhoplex AC-22 (a non-ionic acrylic resin emulsion containing 44-45 weight percent solids, produced by Rohm & Haas Co.) was added to the clay dispersion and ballmilled overnight. The Rhoplex AC-22 was found to have an initial 60 second methanol absorption per double sided area of 6.1 mg/cm The formulation was coated on Dittcopy paper using a No. 16 Mayer bar and dried in an oven at 48C. Copies were prepared by the first mentioned method in Example I and had significantly improved color density, resolution and wash resistance in comparison to copies made on uncoated Dittcopy paper.

EXAMPLE VII Both sides of Dittcopy paper can be coated in accordance with the method of Example I and used in a commercial duplicating machine to obtain high quality images from a master sheet. After drying, the paper can be turned over and replaced in the machine and a different master sheet used to duplicate additional high quality images on the reverse side of each sheet.

We claim:

1. In a spirit method for making dye transfer copies wherein a volatile solvent for said dye is applied to a copy sheet, said copy sheet is contacted while moist with said solvent with a master surface having a design formed thereon of said dye and said copy sheet is separated from said master surface, the improvement, for making copies of improved quality, in which said copy sheet is obtained by:

dispersing particulate material throughout a waterinsoluble organic polymer binder therefor, said organic polymer being emulsified in hydrophilic medium and having an initial 60 second methanol absorption per double sided area in the range of 1.5-8.0 mg/cm said particulate material being capable of adsorbing organic solvent-soluble dye; applying said particulate material-polymer dispersion, in the form of an emulsion of said organic polymer in a hydrophilic medium, to a surface of said copy sheet to form a dry, hydrophilic organic polymer coating of said particulate materialpolymer on said copy sheet surface of greater smoothness and decreased porosity, relative to said copy sheet surface when uncoated, but of high dye absorptivity. 2. The improvement according to claim 1 including the additional step in obtaining said copy sheet of applying said particulate material-polymer dispersion to the reverse side of said copy sheet and calendering to form a dry, hydrophilic organic polymer surface coating thereof of greater smoothness and decreased porosity, relative to said reverse copy sheet surface when uncoated, on said reverse side.

3. The improvement according to claim 2 including the steps following said formation of reverse side coating, of:

applying volatile dye transfer solvent to the coated surface on said reverse copy sheet side;

contacting said reverse side coated surface, while moist with said volatile solvent, with a second master surface having a design formed thereof of dye soluble in said solvent; and

separating said copy sheet from said second master surface.

4. The improvement according to claim 1 in which said particulate material has an average particle size distribution of from about 0.1 micron to about 25 microns.

5. The improvement according to claim 1 in which the ratio of said particulate material to said polymer is 10 about 0.5:1 to about 15:1.

6. The improvement according to claim 1 in which said coating on said copy sheet has a thickness of from about 0.1 mil to about 1.5 mils.

7. The improvement according; to claim 6 in which said particulate material has an average particle size distribution of from about 0.1 micron to about 25 microns and the ratio of said particulate material to said polymer is about 0.5:1 to about 15:1.

8. The improvement according to claim 1 in which said particulate material comprises substantially a silicate pigment clay.

9. The improvement according to claim 1 in which said coated copy sheet surface is calendered to provide microporosity thereto.

10. The improvement according to claim 1 in which said coated copy sheet surface is calendered to texture said coated surface with a continuous plurality of ridges defining discrete depressed regions, opposed portions of said ridges being spaced a distance of about 0.] to 25 microns.

11. The improvement according to claim 10 in which said depressed regions are about 0.1 to 12.5 microns deep.

12. The improvement according to claim 1 in which said copy sheet is coated as part of a stock of coated sheets substantially prior in time to application of said @3 3 UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION d g Dated ogtg'beng J91 ,JI"

- l fls) Joseph Gaynor, Yoshikezu Yamada, Joseph Tat-Him Sund Patent No. Q 930 J, JJ

It iscertified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 20, change "thg-zr'eof to --thereon--.

Signed and sealed this 3rd day. of December 1974. Q

(SEAL) Attest:

McCOY M. ciasou JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. IN A SPIRIT METHOD FOR MAKING DYE TRANSFER COPIES WHEREIN A VOLATILE SOLVENT FOR SAID DYE IS APPLIED TO A COPY SHEET, SAID COAPY SHEET IS CONTACTED WHILE MOIST WITH SAID SOLVENT WITH A MASTER SURFACE HAVING A DESIGN FORMED THEREON OF SAID DYE AND SAID COPY SHEET IS SEPARATED FROM SAID MASTER SURFACE, THE IMPROVEMENT, FOR MAKING COPIES OF IMPROVED QUALITY, IN WHICH SAID COPY SHEET IS OBTAINED BY: DISPERSING PARTICULATE MATERIAL THROUGHOUT A WATER-INSOLUBLE ORGANIC POLYMER BINDER THEREFOR, SAID ORGANIC POLYMER BEING EMULSIFIED IN HYDROPHILIC MEDIUM AND HAVING AN INITIAL 60 SECOND METHANOL ABSORPTION PER DOUBLE SIDED AREA IN THE RANGE OF 1.5-8.0 MG/CM2, SAID PARTICULATE MATERIAL BEING CAPABLE OF ADSORBING ORGANIC SOLVENTSOLUBLE DYE; APPLYING SAID PARTICULATE MATERIAL-POLYMER DISPERSION, IN THE FORM OF AN EMULSION OF SAID ORGANIC POLYMER IN A HYDROPHILIC MEDIUM, TO A SURFACE OF SAID COPY SHEET TO FORM A DRY, HYDROPHILIC ORGANIC POLYMER COATING OF SAID PARTICULATE MATERIAL-POLYMER ON SAID COPY SHEET SURFACE OF GREATER SMOOTHNESS AND DECREASED POROSITY, RELATIVE TO SAID COPY SHEET SURFACE WHEN UNCOATED, BUT OF HIGH DYE ABSORPTIVITY.
 2. The improvement according to claim 1 including the additional step in obtaining said copy sheet of applying said particulate material-polymer dispersion to the reverse side of said copy sheet and calendering to form a dry, hydrophilic organic polymer surface coating thereof of greater smoothness and decreased porosity, relative to said reverse copy sheet surface when uncoated, on said reverse side.
 3. The improvement according to claim 2 including the steps following said formation of reverse side coating, of: applying volatile dye transfer solvent to the coated surface on said reverse copy sheet side; contacting said reverse side coated surface, while moist with said volatile solvent, with a second master surface having a design formed thereof of dye soluble in said solvent; and separating said copy sheet from said second master surface.
 4. The improvement according to claim 1 in which said particulate material has an average particle size distribution of from about 0.1 micron to about 25 microns.
 5. The improvement according to claim 1 in which the ratio of said particulate material to said polymer is about 0.5:1 to about 15:1.
 6. The improvement according to claim 1 in which said coating on said copy sheet has a thickness of from about 0.1 mil to about 1.5 mils.
 7. The improvement according to claim 6 in which said particulate material has an average particle size distribution of from about 0.1 micron to about 25 microns and the ratio of said particulate material to said polymer is about 0.5:1 to about 15:
 8. The improvement according to claim 1 in which said particulate material comprises substantially a silicate pigment clay.
 9. The improvement according to claim 1 in which said coated copy sheet surface is calendered to provide microporosity thereto.
 10. The improvement according to claim 1 in which said coated copy sheet surface is calendered to texture said coated surface with a continuous plurality of ridges defining discrete depressed regions, opposed portions of said ridges being spaced a distance of about 0.1 to 25 microns.
 11. The improvement according to claim 10 in which said depressed regions are about 0.1 to 12.5 microns deep.
 12. The improvement according to claim 1 in which said copy sheet is coated as part of a stock of coated sheets substantially prior in time to application of said solvent. 